Apple's only mistake with the new Air, IMO, is not keeping the old keyboard. I'm right on the verge of needing a new laptop and I'm eagerly looking at a MacBook Air 2018; the keyboard gives me pause, just because it's different than what I'm used to. But the Air name alone, the form factor, and how it's built is basically perfect for me. It does everything I need and then some without making me wait.
As to which you should be choosing though...that is a tough one. The MBP line doesn't feel as unique as it used to, as the price point is just too high for me to justify it to anyone, and the low-end MBPs are basically just heavier MacBook Airs.
(I wouldn't be surprised to see a new keyboard design roll out across some Mac laptops as early as this year, but if it does, it won't come to the Air for a while. Also, I wouldn't be surprised if the new design is still optimized for extreme thinness.)
It's also wonderful that when I need a new machine it's just $350.
Most people still have usb a peripherals, so the laptop situation is confusing. I do podcasting and had to advise someone in the industry on the i/o of new macbooks, it's not obvious for most.